Siloxane resins of the general formula RnSiO(4-n)/2, where R is an alkyl group and n is generally less than 1.8, are an important family of silicone polymers because of their utility in many commercial applications such as adhesive compositions and coatings applications. One particular subclass of siloxane resins, known as MQ resins (since they comprise primarily of “M” units of the general formula R3SiO1/2 and “Q” units of the general formula SiO2), have found utility in cosmetic formulations. In particular MQ resins are commonly used in “extended wear” or “transfer resistant” cosmetic formulations. In these formulations, MQ resins enhance the substantivity of the pigments or other formulation actives to skin after application creating a longer lasting, and hence extended wear product.
Representative examples of transfer resistant cosmetic compositions using MQ resins are found in U.S. Pat. Nos. 6,071,503, 6,074,654, 6,139,823, 6,340,466, WO 97/17058, and WO 97/17059 which disclose compositions comprising the combination of organosiloxane resins and fluid diorganosiloxane resins with a volatile carrier.
Silsesquioxane resins of the general formula RSiO3/2 have also been used as additives in personal care formulations for a variety of functions. For example, in U.S. Pat. No. 5,733,537 by Halloran teaches the use of a non-polar silsesquioxane resin as a hair fixative. U.S. Patent application publication 20030086888 by Legrow discloses trimethylsilyalkylsilsesquioxanes in leave-on compositions for personal care. More recently, U.S. provisional application 60/514,001 and 60/541,002, as filed by the same assignee as the present application, discloses MQ-propyl resins compositions and use in a variety of personal care formulations. Also, U.S. provisional application 60/553,450, as filed by the same assignee as the present application, discloses alkyl-phenyl silsesquioxane resins in a variety of personal care applications.
While these references represent advances in the art, there is still a need for improved siloxane resins for use in skin care formulations that offer extended durability to cosmetic formulations, but also provide other functional benefits, such as moisturization, occlusivity, and improved feel. Furthermore, there is a need for siloxane resins having wax like characteristics, but yet still possess solubility in commonly used personal care solvents, including volatile silicones
The present inventors have discovered improved siloxane resins by incorporating two distinct hydrocarbon groups in a silsesquioxane resin. The first hydrocarbon has 1 to 8 carbon atoms, and the second hydrocarbon group has 9-40 carbon atoms. The resulting siloxane resins, herein referred to as silsesquioxane resin wax, improve the durability and substantivity of cosmetics after topical application to skin, improved the non transfer of color cosmetic formulations such as castor oil based lipsticks and have improved compatibility over other silicone waxes in cosmetic ingredients and fragrances while also providing other functional benefits such as moisturization, occlusivity, and improved feel. These silsesquioxane resin waxes can also act as texture and rheology modifiers in water-in-oil and oil-in-water emulsions. The melting points and overall hydrocarbon content of the silsesquioxane resins can be adjusted to provide varying aesthetic benefits from a personal care formulation. The silsesquioxane resin wax can also be used in personal care formulations to improve fragrance retention and delivery of actives.